Varying Protein Content and Nitrogen Solubility for Pluriparous,Lactating Holstein Cows: Lactation Performance and Profitability

Effects on total lactation performance of varying ration crude protein (15.3 vs. 13.6% of dry matter) and nitrogen solubility (35 vs. 45% of total nitrogen) in early lactation was studied using 57 pluriparous Holstein cows. Grain was fed according to production so as to minimize change in body weight throughout lactation. Forages high in nitrogen solubility, corn and grass silages, were fed free-choice. Percent concentrate in ration dry matter was highest (64%) 5 to 8 wk postpartum and lowest (3%) 33 to 44 wk postpartum. Protein and nitrogen solubility were varied by formulating four protein supplements fed as 10% of the grain allocation, so differences in treatments applied narrowed as lactation progressed. Cows fed the medium-protein diets produced 196 kg more milk than those receiving low-protein diets, but their peak daily milk yield was only .6 kg higher. Cows receiving rations with reduced nitrogen solubility produced 347 kg more milk than those fed the higher solubility diets, but their peak daily milk yield was 1.0 kg lower. Income above fed cost for the lactation was highest and postpartum loss in body weight was least for cows receiving medium-protein and low-solubility rations in early lactation, but no differences were significant. Both milk yield (38.3 to 40.6 kg) and total dry matter intake (3.74 to 3.91% body weight) means were maximum 6 to 7 wk postpartum, but lactation performance was not proportional to peak milk yield. When cows are fed to minimize body fat mobilization, response to increased protein in the diet is small. Reducing nitrogen solubility of silage-based diets increased milk produced per unit grain fed. There were no adverse effects of treatments on breeding efficiency or herd health.     

Exogenous β-mannanase improves feed conversion efficiency and reduces somatic cell count in dairy cattle

Exogenous fibrolytic enzymes have been shown to be a promising way to improve feed conversion efficiency (FCE). β-Mannanase is an important enzyme digesting the polysaccharide β-mannan in hemicellulose. Supplementation of diets with β-mannanase to improve FCE has been more extensively studied in nonruminants than in ruminants. The objective of this study was to investigate the effects of β-mannanase supplementation on nutrient digestibility, FCE, and nitrogen utilization in lactating Holstein dairy cows. Twelve post-peak-lactation multiparous Holstein cows producing 45.5 ± 6.6 kg/d of milk at 116 ± 19.0 d in milk were randomly allotted to 1 of 3 treatments in a 3 × 3 Latin square design with 3 periods of 18 d (15 d for adaptation plus 3 d for sample collection). All cows were fed the same basal diet and the 3 treatments differed only by the β-mannanase dose: 0% dry matter (DM; control), 0.1% of DM (low supplement, LS), and 0.2% of DM (high supplement, HS) supplemented to the basal diet. Supplementation of β-mannanase enzyme at the LS dose reduced dry matter intake (DMI) but did not affect milk yield or milk composition. Cows receiving LS produced 90 g more milk per kg of DMI compared with control cows. Somatic cell count (SCC) in milk was lower for cows fed the LS diet compared with cows fed control diets. Cows fed LS diet had lower DM, organic matter and crude protein digestibility compared with cows fed control diets. Starch, neutral detergent fiber, and acid detergent fiber digestibility were not affected by LS. Milk yield, DMI, SCC, and nutrient digestibility did not change for HS. Despite the reduced crude protein digestibility, reduced N intake led to similar fecal N excretions in LS cows and control cows (234 vs. 235 g/cow per day). Urinary N excretions remained similar between enzyme-fed and control cows (~190 g/cow per day), although the percentage of N intake partitioned to urinary N tended to be greater in LS than in control cows (31 vs. 27%). Cows fed LS significantly improved the percentage of apparently absorbed N partitioned to milk protein N (42 vs. 38%). When supplemented at 0.1% of dietary DM, β-mannanase can improve FCE and lower the SCC of dairy cows without affecting milk yield, milk composition, or total manure N excretions of dairy cows.     

A comparison of serum metabolic and production profiles of dairy cows that maintained or lost body condition 15 days before calving

Body condition score (BCS) change is an indirect measure of energy balance. Energy balance before calving may affect production and health in the following lactation. It is likely that cows may experience BCS loss before calving due to negative energy balance. The objective of this study was to determine if loss of BCS 15 d before calving affected milk production, BCS profile, and metabolic status during the transition period and early lactation. On d ?15 to d 0 relative to calving, BCS was assessed (1 = emaciated, 5 = obese) for 98 Holstein-Friesian cows. The cows were divided into 2 groups: those that did not lose BCS between d ?15 and d 0 (maintained, BCS-M, n = 55) and those that lost BCS from d ?15 to d 0 (lost, BCS-L, n = 43, average loss of 0.29 ± 0.11 BCS). The fixed effects of BCS group, parity, week (day when analyzing milk production records), their interactions, and a random effect of cow were analyzed using PROC MIXED of SAS (SAS Institute Inc., Cary, NC). Before calving, BCS-L cows tended to have higher concentrations of nonesterified fatty acids than BCS-M cows (0.88 vs. 0.78 mmol/L). After calving, BCS-L cows had higher nonesterified fatty acid concentrations in wk 1 (0.93 vs. 0.71 mmol/L), wk 2 (0.84 vs. 0.69 mmol/L), and wk 4 (0.81 vs. 0.63 mmol/L) than BCS-M cows. The BCS-L cows had higher concentrations of β-hydroxybutyrate (BHB) in wk 1 (0.72 vs. 0.57 mmol/L), wk 2 (0.97 vs. 0.70 mmol/L), and wk 4 (0.94 vs. 0.67 mmol/L) compared with BCS-M cows. We detected significant reductions in insulin concentrations in BCS-L cows from wk ?1 (2.23 vs. 1.37 µIU/mL) to wk 2 (1.68 vs. 0.89 µIU/mL) and wk 4 (2.21 vs 1.59 µIU/mL) compared with BCS-M cows. Prevalence of subclinical ketosis increased in BCS-L cows in wk 3 and 4 when BHB was ≥1.4 mmol/L and in wk 1, 3, and 4 when BHB was ≥1.2 mmol/L. In wk 1, BCS-L cows tended to have lower levels of calcium than BCS-M cows (2.33 vs. 2.27 mmol/L). We found no differences between the groups of cows for milk yield and energy-corrected milk. The BCS-L cows had lower BCS up to 75 d in lactation. Overall, BCS-L cows had higher somatic cell scores with an elevated somatic cell score on d 45, d 60, and d 75. There was an overall tendency for BCS-L cows to have higher fat yield and an overall significant increase in fat percentage. Overall, BCS-L cows had lower lactose percentage, with a reduction on d 60. This work shows that BCS loss before calving may have significant consequences for metabolic status, milk composition, somatic cell score, and BCS profile in dairy cows.     

Lactational and Systemic Responses to the Supplementation of Protected Methionine in Soybean Meal Diets

Twenty-seven Holstein cows (14 primiparous and 13 multiparous) were randomly assigned to diets containing soybean meal without or with 15 g of added DL-methionine daily, provided as 50 g of ruminally protected methionine product, during wk 4 through 16 postpartum. Cows were fed a 15.3% crude protein total mixed diet of (dry matter basis) 30% corn silage, 15% alfalfa hay, and 55% concentrate mix. Yields of milk (32.9 and 35.2 kg/d), 4% fat-corrected milk (27.8 and 29.5 kg/d), and solids-corrected milk (28.5 and 30.1 kg/d) were higher for cows fed supplemental methionine. Milk protein percentage (2.99 and 3.06) was increased with supplemental methionine, while the percentage of fat (2.96 and 3.00), solids-not-fat (8.69 and 8.73), and total solids (11.67 and 11.71) were similar among diets. Dry matter intake (19.3 and 21.3 kg/d) was higher with methionine supplementation. Ruminal pH, volatile fatty acids, ammonia, and serum urea were generally unaffected by methionine supplementation. Concentrations of methionine in arterial and venous serum were elevated slightly by methionine supplementation, but the first-limiting amino acid for milk production, as calculated by several methods, was not changed.     

Feeding Value of Dry Corn,Ensiled High Moisture Corn,and Propionic Acid Treated High Moisture Corn Fed with Hay or Haylage for Lactating Dairy Cows

Trial 1. Fifty lactating Holstein and Brown Swiss cows were assigned to six groups in a 3 × 2 factorial design and fed one of six diets for 16 wk: (1) dry corn + hay, (2) dry corn + haylage, (3) ensiled high moisture corn + hay, (4) ensiled high moisture corn + haylage, (5) propionic acid treated corn + hay, and (6) propionic acid treated corn + haylage. Quantities equal in dry matter of dry corn, ensiled corn, and acid treated corn were offered in the ratio of 1 kg concentrate (corn and supplement) for each 2.75 kg milk produced. Forage was fed free choice. Means adjusted by covariance for cows fed diets 1 to 6 averaged: dry matter intake (kg/day), 16.7, 20.0, 17.4, 20.6, 17.1, 20.0; 4% fat-corrected milk (kg/day), 21.8, 21.1, 22.6, 23.5, 22.4, 23.4; milk fat percent, 3.54, 3.45, 3.63, 3.53, 3.62, 3.80; and acetate to propionate ratio 3.53, 3.85, 3.73, 3.66, 3.13, 3.32. Cows fed ensiled corn and acid treated corn produced more 4% fat-corrected milk than did cows fed dry corn. The molar percent acetate to propionate ratio in rumen fluid of cows fed acid treated corn was lower than for cows fed dry corn or ensiled corn.Trial 2. Dry corn or propionic acid treated corn was fed to 12 cows in combination with a supplement, 4.54 kg of hay, and ad libitum haylage. Means adjusted by covariance for cows fed dry corn and acid treated corn averaged: dry matter intake (kg/day), 18.2 and 17.7; 4% fat-corrected milk (kg/day), 20.6 and 20.1; and total digestible nutrients (%) 63.7 and 58.7.Any of these methods are acceptable for storing corn, and feeding this corn in properly supplemented diets will yield acceptable lactation performance.     

Influence of Pecan Shells and Hulls as a Roughage Source on Milk Production,Rumen Fermentation,and Digestion in Ruminants,

In Experiment 1, 20 lambs (36 kg) were fed five diets containing 0, 5, or 10% pecan shells or hulls to evaluate digestion and nitrogen balance. Digestion was not depressed by diets containing 5% shells. Protein digestibility was not reduced and nitrogen balance was higher for lambs fed 5% hulls than for lambs in other groups. In Experiment 2, 8 Holstein cows (29.3 kg milk/d) were assigned to two diets: basal and basal with 5% shells in the grain mix. Cows fed diets containing shells produced the same amount of milk and milk fat as control cows. In Experiment 3, 12 Holstein cows (27.3 kg milk/d) were assigned to the same two diets used in Experiment 2 and a third treatment received 5% pecan hulls in the grain mix. Cows fed shells or hull diets reduced concentrate intake and milk production. In Experiment 4, 12 Hereford × Angus steers (474.5 kg) were fed diets used in Experiment 3 to examine rumen fermentation, digestion, and passage rates. Steers fed hulls had lower rumen ammonia N and higher rumen pH compared with steers fed the basal diet. Total rumen volatile fatty acid concentration was not different among treatments. Generally, rumen fluid from steers fed hulls had higher proportions of acetate and lower porportions of butyrate. Rumen fluid and particulate passage rates and digestion measurements were not affected by addition of shells or hulls.     

Brown Midrib Corn Silage in Dairy Cattle Rations,

Two groups of 12 Holstein cows past peak lactation were fed complete mixed diets containing either brown midrib corn silage or its normal genetic counterpart. All cows were fed a standardization ration containing another corn silage prior to and after the experimental period. Performance during the experimental period was expressed as deviation from standardization. Cows fed brown midrib silage produced .66 kg more milk per day that tested .28 percentage units less fat during the 4-wk experimental period than during standardization. Control cows produced .10 kg more milk per day in the experimental period as compared to standardization without difference in fat test. On a fat-corrected basis (4%) there was no difference in milk yield between treatments.     

Effect of Feeding Frequency on Diurnal Dry Matter and Water Consumption,Liquid Dilution Rate,and Milk Yield in First Lactation

Four ruminally cannulated cows in first lactation (50 days postpartum) were assigned randomly to a 4 × 4 Latin square with the following feeding frequencies of the same total mixed ration: one, two, four, and eight times a day. Dry matter intake, water consumption, and ruminal pH were recorded hourly during 4-d collection (10-d adaptation between periods, Experiment 1). In Experiment 2, 30 animals were blocked by milk production on wk 4 postpartum and assigned to feeding one or four times a day through wk 19 postpartum. Individual feed consumption and milk production were recorded daily.Hourly consumption patterns of dry matter and water were variable over 24 h; once daily feeding tended to be more variable than other frequencies. Cows fed four times a day had higher ruminal liquid dilution rates than those fed eight times; feeding once and twice a day was not different from either. In Experiment 2, frequency of feeding total mixed ration had no significant influence on dry matter intake or milk yield; however, cows fed four times a day exhibited a consistent weekly tendency to be lower in dry matter intake and higher in milk yield than those fed once daily. Efficiency of fat-corrected milk production was slightly higher for cows fed four times than for those fed once daily.     

Induction of Lactation by Two Techniques: Success Rate,Milk Composition,Estrogen and Progesterone in Serum and Milk,and Ovarian Effects

Induction of lactation was attempted in 12 heifers and 12 cows with estradiol benzoate (.011 mg/kg body weight per day) subcutaneous for 10 days or that plus progesterone (.1 mg + .25 mg/kg body weight per day) for 7 days. Milking commenced on day 20 for those treated with the mixture and on day 11 for the others. Lactations were induced (minimum of 4.5 kg of milk/day) in five of six heifers and two of six cows by the mixture and in six of six heifers and three of six cows for estradiol benzoate. Milk production was 44% of herdmates in the 16 induced lactations. Cows on the single treatment had lower production than the other three groups. Ovarian status, cycling, cystic, or static, was affected adversely in 5 of 16 animals induced successfully. Two of the 16, both heifers, carried calves to term following induction. The transition to normal composition of milk was slower for single than double treatment. Lactose increased slowly to normal over the 1st wk of milking while protein decreased slowly. Estrogen and progesterone in milk of induced cows were approximately twice as concentrated as in normal post-parturient cows, probably because milk production was halved.     

Forage Growth and Performance of Grazing Dairy Cows Fed Concentrates with or Without Sodium Bicarbonate

Groups of 12 and 13 Holstein cows grazed rotarionally on mixtures of grasses and red clover. Cows were 28 to 150 days into lactation at start of the experiment. They were fed concentrate at 1 kg/3 kg of 4% fat-corrected milk with or without 1.9% sodium bicarbonate in a switchover trial of two 8-wk periods. Forage growth and composition, amounts available for grazing, and average intake were measured by subsamples clipped prior to and after each grazing and by use of cages placed in the field. Milk yields averaged 29.9 kg daily by cows on each treatment. Milk fat percentage decreased moderately when cows first went to pasture but were not different during the trial at 3.24 and 3.27% on control and buffer treatments. Milk protein percentages, proportions of ruminal volatile fatty acids, and body weight gains did not differ with treatment. Available forage exceeded 17 kg dry matter per cow daily. It was of good quality, as indicated by crude protein contents of 19 and 22%, acid detergent fiber less than 35%, and 67 to 70% in vitro digestibility. Average intake of forage dry matter, measured by the sward cutting technique, was 12.6 kg per cow daily over the 16 wk.     

Automatic Individual Feeding of Concentrates to Dairy Cattle

Two methods of feeding concentrates according to milk production were compared in a switchback experimental design. Twenty-four cows were assigned to two groups and the groups balanced according to age, milk production, fat-corrected milk production, and body weight. The cows were fed individually their daily allowance of concentrate while in the milking parlor or with an electronic feeder which dispersed concentrates at any hour of the day. All cows received corn silage in a feed bunk. Daily milk production increased .71 kg when cows were fed concentrates electronically. However, there were no significant differences in daily concentrate intake, production of fat-corrected milk, butter-fat percentage, or solids-not-fat percentage for the two treatments.     

Protected Methionine and Heat-Treated Soybean Meal for High Producing Dairy Cows

Twenty-four high producing Holstein cows (14 primiparous and 10 multiparous) were fed concentrate mix containing heat-treated soybean meal without or with 15 g of added DL-methionine daily provided as 50 g of ruminally protected methionine product during wk 4 through 16 postpartum. The 15% crude protein mixed diets contained 30% (dry matter basis) corn silage, 15% alfalfa hay, and 55% concentrate mix. Covariant adjusted yields of milk (34.6 and 33.1 kg/d), 4% fat-corrected milk (28.4 and 27.6 kg/d), and solids-corrected milk (29.0 and 28.5 kg/d) were not increased by feeding supplemental methionine. Percentages of fat (2.81 and 2.92) and protein (2.88 and 2.92) were similar, whereas total solids (11.49 and 12.69) and solids-not-fat (8.68 and 8.77) were higher with supplemental methionine. Dry matter intakes (20.2 and 21.0 kg/d) were higher when cows were fed supplemental methionine. Ruminal pH, volatile fatty acids, and ammonia as well as blood serum urea and glucose were generally unaffected by methionine supplementation. Concentrations of methionine in arterial and venous plasma were elevated slightly when additional methionine was fed. The first-limiting amino acid for milk production, methionine, was calculated by several methods and was not changed by feeding supplemental ruminally protected methionine.     

Effect of acarbose on milk yield and composition in early-lactation dairy cattle fed a ration to induce subacute ruminal acidosis

Subacute ruminal acidosis reduces lactation performance in dairy cattle and most often occurs in animals fed a high concentrate:forage ration with large amounts of readily fermentable starch, which results in increased production of volatile fatty acids and lactic acid and a reduction in ruminal pH. Acarbose is commercially available (Glucobay, Bayer, Wuppertal, Germany) and indicated for the control of blood glucose in diabetic patients. In cattle, acarbose acts as an α-amylase and glucosidase inhibitor that slows the rate of degradation of starch to glucose, thereby reducing the rate of volatile fatty acid production and maintaining rumen pH at higher levels. The ability of acarbose to reverse the reduced feed intake and milk fat percentage and yield associated with a high concentrate:forage ration with a high risk of inducing subacute ruminal acidosis was evaluated in 2 experiments with lactating dairy cattle. In 2 preliminary experiments, the effects of a 70:30 concentrate:forage ration on ruminal pH and lactation were evaluated. Ruminal pH was monitored in 5 Holstein steers with ruminal cannulas every 10 min for 5 d. Ruminal pH was <5.5 for at least 4 h in 79% of the animal days. In dairy cows, the 70:30 concentrate:forage ration decreased feed intake 5%, milk fat percentage 7%, and milk fat yield 8% compared with a 50:50 concentrate:forage ration but did not affect milk yield. Early lactating dairy cattle were offered the 70:30 concentrate:forage ration with 0 or 0.75 g/d of acarbose added in a crossover design in 2 experiments. In the first experiment, acarbose increased dry matter feed intake (23.1 vs. 21.6 kg/d) and 3.5% fat-corrected milk yield (33.7 vs. 31.7 kg/d) because of an increase in percentage milk fat (3.33 vs. 3.04%) compared with control cows. In the second experiment, cows were fasted for 3 h before the morning feeding to induce consumption of a large meal to mimic conditions that might be associated with unplanned delayed feeding. In this experiment, acarbose also increased feed intake (22.5 vs. 21.8 kg/d) and 3.5% fat-corrected milk yield (36.9 vs. 33.9 kg/d) due to increased percentage milk fat (3.14 vs. 2.66%) compared with controls. Thus, acarbose reversed the decreased feed intake and low milk fat percentage and yield associated with feeding a high concentrate:forage ration shown to induce subacute ruminal acidosis in Holstein steers.     

Alkali-Treated Forage for Early Lactation Dairy Cows: Effect on Lactation Performance and Nutrient Digestibility

Our objective was to determine the effect of sodium hydroxide treatment (4 g NaOH/100 g forage DM) of an alfalfa-orchardgrass forage and its subsequent utilization by early lactation dairy cows. Forage was harvested as hay. Complete mixed diets consisted of 55% control or treated hay and 45% concentrate (DM basis) and were fed to eight early lactation Holstein cows in a crossover design. Chemical composition of hays and complete diets were similar. Intake of dry matter was greater when cows were fed treated hay (23.4 vs. 22.2 kg/d), as was milk yield (32.3 vs. 30.9 kg/d). Yield of 4% FCM, however, did not differ between diets (27.8 vs. 27.4 kg/d). Cows fed the treated hay diet had increased concentrations of total rumen volatile fatty acids and ruminal acetate, decreased ruminal isobutyrate concentration and pH, and increased apparent digestibility of NDF, ADF, hemicellulose, and lignin. Sodium hydroxide treatment also increased the proportion of potentially digestible DM and NDF compared with that of untreated forage. Alkali treatment improved the utilization of medium quality forage in the early lactation dairy cow.     

Forage Growth and Performance of Grazing Dairy Cows Supplemented with Concentrate and Chopped or Long Hay

Holstein and Brown Swiss cows were in three groups of eight in a 3 × 3 Latin square design with 4-wk periods. Cows averaged 88 d in lactation at start of trial. All cows simultaneously grazed grass and clover pastures on a rotational basis. Supplement treatments were concentrate (A), concentrate with 10% added chopped hay (B), and concentrate plus 1 kg long hay/cow daily (C). Concentrate was offered at 1 kg/3 kg 4% fat-corrected milk to cows on A and C, and 1 kg/2.7 kg to those on B. Forage growth, amounts available for grazing, and average dry matter intake were measured by clipping subsamples prior to and after each grazing and by use of cages placed in the field.Milk yields and milk fat percentages were 27.1, 3.34; 27.9, 3.32; and 28.3, 3.20 for treatments A, B, and C, respectively. Differences between A and C were significant. Milk fat percentage decreased moderately when cows first went to pasture.There were no treatment differences in fat yield, milk protein percentage, yield of fat-corrected milk, rumen fluid composition, or body weight gain.Available forage per cow exceeded 22 kg dry matter/cow daily except during one 10-d period toward the end of the trial when it amounted to 16.6 kg. Intake of dry matter from pasturage, measured by the sward cutting technique, averaged 14.5 kg./cow daily over the 12 wk.     

Effect of dry period length on milk yield over multiple lactations

Shortening or omitting the dry period (DP) can improve the energy balance of dairy cows in early lactation through a decrease in milk yield after calving. Little is known about the effect of a short or no DP on milk yield over multiple lactations. Our objectives were (1) to assess the effect of DP length over multiple lactations on milk yield, and (2) to assess if the prediction of milk yield in response to DP length could be improved by including individual cow characteristics before calving. Lactation data (2007 to 2015) of 16 Dutch dairy farms that apply no or short DP were used to compute cumulative milk yield in the 60 d before calving (additional yield) and in the 305 d after calving (305-d yield), and the mean daily yield over the interval from 60 d before calving to 60 d before next calving (effective lactation yield). The DP categories were no (0 to 2 wk), short (3 to 5 wk), standard (6 to 8 wk), and long (9 to 12 wk). The effect of current DP and previous DP on yields was analyzed with mixed models (n = 1,420 lactations). The highest effective lactation yield of fat- and protein-corrected milk (FPCM) was observed for cows with a standard current DP (27.6 kg per day); a daily decrease was observed of 0.6 kg for a long DP, 1.0 kg for a short DP, and 2.0 kg for no DP. Previous DP did not significantly affect the effective lactation yield. Thus, cows can be managed with short or no DP over consecutive lactations without a change in quantity of milk losses. Cows that received no DP for consecutive lactations had a lower additional yield before calving (?172 kg of FPCM), but a higher 305-d yield (+560 kg of FPCM), compared with cows that received no DP for the first time. This could lessen the improvement of the energy balance in early lactation when no DP is applied a second time compared with the first time. For the second objective, a basic model was explored to predict effective lactation yield based on parity, DP length, and first-parity 305-d yield (n = 2,866 lactations). The basic model was subsequently extended with data about recent yield, days open, and somatic cell count. Extending the model reduced the error of individual predictions by only 6%. Therefore, the basic model seems sufficient to predict the effect of DP length on effective lactation yield. Other individual cow characteristics can still be relevant, however, to make a practical and tailored decision about DP length.     

Influence of Pelleting Whole Cottonseed on Ration Digestibility and Milk Production and Composition

Two trials were conducted to determine the effect of pelleting whole cottonseed on milk production and composition and ration digestibility. In trial 1, four multiparous Holstein cows were paired by production and used in a 2 × 2 reversal design with 37-d experimental periods. Cow receiving pelleted cottonseed produced 35.12 kg/d milk and 31.74 kg/d of 4% fat corrected milk as compared with 33.41 and 29.83 for cows receiving whole cottonseed. There were no significant differences in dry matter intake or milk composition between treatments. Yield of total solids and lactose was greater for cows receiving pelleted cottonseed as compared with whole cottonseed. Apparent digestibility coefficients for dry matter, gross energy, and crude protein were not different due to pelleting.In trial 2, four ruminal and abomasally cannulated Holstein steers were paired in a 2 × 2 reversal design and fed either pelleted on whole cottonseed for 10 d followed by a 7-d collection. Steers receiving the pelleted cottonseed had higher intakes of gross energy and crude protein. There were greater amounts of total crude protein and crude protein in the particulate phase of abomasal digesta from steers receiving pelleted cottonseed as compared with whole cottonseed. Apparent digestibility for crude protein for the whole tract was not different due to treatment.     

Persistence of chlorpyrifos-methyl in corn silage and effects of feeding dairy cows the treated silage

Corn was sprayed in the field at dent stage of maturity with chlorpyrifos-methyl [O, O,-dimethyl O-(3, 5, 6-trichloro-2-pyridyl) phosphorothioate] at .56, 1.12, and 2.24 kg per hectare, ensiled 1 day later, and methodology for detection of residues was developed. Losses of total residues (chlorpyrifos-methyl and its pyridinol hydrolysis product) through 83 days of ensiling were equivalent to 55, 71, and 76% of that applied. Beginning 83 days post ensiling, control and treated silages were fed to 16 cows, 4 per treatment, for 42 days during which chlorpyrifos-methyl averaged .35, .87, and 1.85 ppm, and was stable. The pyridinol averaged .44, .79, and 1.75 ppm but continued to decline and during the last week of feeding averaged only 32% of that in silage fed the 1st wk. Residue intakes amounted to .009, .022, and .054 mg chlorpyrifos-methyl and .012, .020, and .051 mg of pyridinolk/g body weight and failed to affect silage intake, milk production, blood cholinesterase activity, or body weight gains. Traces of chlorpyrifos-methyl (.003 ppm or less) were only in milk from cows on the 2.24 kg treatment. Milk from all cows fed treated silage contained traces of the pyridinol (.011 ppm or less). No trace of the O-analog of chlorpyrifos-methyl was in any sample, and all milk, urine, and feces were free of residues within 1 wk after the cows were withdrawn from treated silage.     

The effect of supplemental concentrate fed during the dry period on morphological and functional aspects of rumen adaptation in dairy cattle during the dry period and early lactation

Ten rumen-cannulated Holstein-Friesian cows were used to examine the effect of feeding supplemental concentrate during the dry period on rumen papillae morphology and fractional absorption rate (k_a) of volatile fatty acids (VFA) during the dry period and subsequent lactation. Treatment consisted of supplemental concentrate [3.0 kg of dry matter (DM)/d] from 28 d antepartum (ap) until the day of calving, whereas control did not receive supplemental concentrate. Cows were fed for ad libitum intake and had free access to the dry period ration (27% grass silage, 28% corn silage, 35% wheat straw, and 11% soybean meal on a DM basis) and, from calving onward, to a basal lactation ration (42% grass silage, 42% corn silage, and 16% soybean meal on a DM basis). From 1 to 3 d postpartum (pp), all cows were fed 0.9 kg DM/d of concentrate, which increased linearly thereafter to 8.9 kg of DM/d on d 11 pp. At 28, 18, and 8 d ap, and 3, 17, 31, and 45 d pp, rumen papillae were collected and k_aVFA was measured in all cows. On average, 13.8 (standard deviation: 3.8) papillae were collected each from the ventral, caudodorsal, and caudoventral rumen sacs per cow per day. The k_aVFA was measured by incubating a standardized buffer fluid (45 L), containing 120 mM VFA (60% acetic, 25% propionic, and 15% butyric acid) and Co-EDTA as fluid passage marker, in the evacuated and washed rumen. Treatment did not affect ap or pp DM and energy intakes or milk yield and composition. Treatment increased papillae surface area, which was 19 and 29% larger at 18 and 8 d ap compared with 28 d ap, respectively. Surface area increased, mainly due to an increase in papillae width. However, treatment did not increase k_aVFA at 18 and 8 d ap compared with 28 d ap. In the control group, no changes in papillae surface area or k_aVFA were observed during the dry period. In the treatment group, papillae surface area decreased between 8 d ap and 3 d pp, whereas no decrease was observed for control. From 3 to 45 d pp, papillae surface area and k_aVFA increased for all cows by approximately 50%, but the ap concentrate treatment did not affect k_aVFA pp. In conclusion, the efficacy of supplemental concentrate during the dry period to increase papillae surface area and k_aVFA in preparation for subsequent lactation is not supported by the present study. Current observations underline the importance of functional measurements in lieu of morphological measurements to assess changes in the adapting rumen wall.     

Effects of Feeding Synthetic Zeolite A and Sodium Bicarbonate on Milk Production Nutrient Digestion,and Rate of Digesta Passage in Dairy Cows

Four rumen-cannulated Holstein cows were fed synthetic zeolite A and NaHCO₃ to evaluate their affect on milk production, nutrient digestibility, rumen fermentation, and rate of digesta passage. Treatments were allocated in a 2 × 2 factorial arrangement within a 4 × 4 Latin-square design. Treatments consisted of control; 1.0% NaHCO₃; 2.0% zeolite; and 1.0% NaHCO₃ plus 2.0% zeolite. A total mixed ration with 50:50 concentrate to forage (80% corn silage, 20% haylage) DM was fed.Intake of DM was lower for cows receiving zeolite (18.7 vs. 20.7 kg/d). Decreases were noted in daily milk (26.3 vs. 28.9 kg/d). 4% FCM (23.6 vs. 25.6 kg/d); milk fat yield (.86 vs. .93 kg/d); milk protein yield (.85 vs. .95 kg/d); and milk protein percent (3.21 vs. 3.34) with zeolite. Digestibilities of DM, organic matter, and crude protein were also decreased by zeolite but ADF digestion was unaffected. Rumen pH was increased, ruminal propionate decreased, and acetate:propionate ratio increased by zeolite. All other VFA plus rumen NH₃ were not affected by treatment. Decreases due to zeolite were observed in liquid fractional rate of passage and liquid flow rate when measured by Cr-EDTA in the feces. No treatment differences were found in fractional rate of passage of feed particles. Addition of NaHCO₃ had no significant effects.